In the related art, there is a heating element that generates heat by an oxidation reaction of an oxidizable metal. The heat generating elements that are configured to contain the oxidizable metal such as iron powder, a carbon component, and water, and that generate heat by the oxidation reaction of the oxidizable metal are disclosed in, for example, Patent Documents 1 and 2.
In Patent Document 1, a heating element using an ink-like or creamy heat generation composition is described. According to the heating element, a generation of dust at the time of manufacturing the heating element is prevented, and a heat generation reaction of a heat generation composition is suppressed, so that it is said that it is possible to prevent loss due to the heat generation reaction at the time of manufacturing, and quality deterioration or solidification of the heat generation composition.
In Patent Document 2, a heating element in which blending of a heat generating layer and a water retaining layer is suitably controlled is described. According to the heating element, abnormal heat generation is prevented even in a case where a heat generation composition is filled in a large amount for some reason or is unevenly distributed in specific locations at the time of manufacturing the heating element, so that it is described that favorable heat generation characteristics can be stably obtained, and that it may be accompanied by generation of steam.